CN204553533U - The precision ball hinge of joint space is detected based on sphere capacitance principle - Google Patents

Abstract

The utility model discloses a kind of precision ball hinge detecting joint space based on sphere capacitance principle.The detection technique in spherical hinge gap is also immature; In electrostatic gyroscope technology, the method for detection rotor center displacement is difficult to the joint space detection being directly used in precision ball hinge.The utility model comprises ball-and-socket, bulb, spherical hinge take-off lever and static plate electrode; Static plate electrode CJ _ibe fixed in ball-and-socket, wherein, i=1,2 ... 8, and be distributed in eight quadrants of three-dimensional system of coordinate and be encircled into sphere; Static plate electrode CJ _ibe equal and opposite in direction and the radius tip electrode concentric with ball-and-socket; Bulb as movable plate electrode, and with static plate electrode CJ _iform eight sphere electric capacity; Spherical hinge take-off lever and bulb are fixed; Static plate electrode CJ _iall insulating material is scribbled with the surface of contact of ball-and-socket.The utility model changes the principle causing output capacitance to change according to the gap between sphere capacitor plate, achieve the real-time non-contact detection of spherical hinge Three Degree Of Freedom center displacement.

Description

The precision ball hinge of joint space is detected based on sphere capacitance principle

Technical field

The utility model belongs to measurement technique field, is specifically related to a kind of precision ball hinge detecting joint space based on sphere capacitance principle.

Background technique

Spherical hinge is a kind of Three Degree Of Freedom mechanical joint generally adopted, and has compact structure, motion flexibly and the advantage such as bearing capacity is strong, becomes the key member in the machinery such as paralleling mechanism, industrial robot and auto parts and components.

Due to reasons such as manufacture, alignment errors, gap must be had to exist between the bulb of spherical hinge and ball-and-socket in actual applications, in the process of spherical hinge transmission campaign and power, inevitably cause take-off lever to produce skew relative to ideal position, thus have impact on the transmission accuracy of system.More to the theoretical research of end effector Accuracy in paralleling mechanism about spherical hinge gap error at present, but the detection technique in its gap is also immature.HeFei University of Technology Hu Penghao etc. find that spherical hinge gap error is relevant with pose to ball pivot bar working space angle under study for action, and relevant to work loads size and Orientation, present the feature of certain space random error; And a kind of precision ball hinge gap detector and method of measurement are proposed in patent CN102607400A, to realize the automatic detection of spherical hinge in three dimensional space internal clearance error.The principle of displacement is detected in bosoms, Tsing-Hua University's fourth sky etc. in patent CN101458076A based on current vortex sensor, propose the system of selection of Sensor location arrangements, can realize the simple and quick process of Spherical Clearance survey data.China Engineering Physics Research Institute Ding Lihua etc. devises a kind of cloth loudspeaker lattice (Bragg) fiber-optic grating sensor measured for Spherical Clearance, by two fiber bragg gratings being pasted onto the sensing probe form that metal clips two sides is made into sheet-like structure, measure for sphere interlayer close gap.

In addition, electrostatic gyroscope technology develops comparatively ripe at home and abroad, its supporting system is suspended in by rotor stability in high vacuum ball chamber by electrostatic force, there is mechanical contact, disturb little, precision advantages of higher, adopt the change of electrode-rotor clearance electric capacity to measure the displacement in rotor comparative electrode ball chamber, realize electrostatic force feedback and control.But the joint space that the method is difficult to be directly used in precision ball hinge is detected.

Summary of the invention

The purpose of this utility model is for the deficiencies in the prior art, a kind of precision ball hinge detecting joint space based on sphere capacitance principle is provided, the Research Thinking of rotor comparative electrode ball chamber displacement is measured in the change of using for reference electrode-rotor clearance electric capacity in electrostatic gyroscope technology, the structure of radius tip electrode and layout are designed, thus accurately detects the gap error of precision ball hinge.

The utility model comprises ball-and-socket, bulb, spherical hinge take-off lever and static plate electrode; Static plate electrode CJ _ibe fixed in ball-and-socket, wherein, i=1,2 ... 8, and be distributed in eight quadrants of three-dimensional system of coordinate and be encircled into sphere; Static plate electrode CJ _ibe equal and opposite in direction and the radius tip electrode concentric with ball-and-socket; Described bulb as movable plate electrode, and with static plate electrode CJ _iform eight sphere electric capacity; Described spherical hinge take-off lever and bulb are fixed; Static plate electrode CJ _iall insulating material is scribbled, as epoxy resin with the surface of contact of ball-and-socket; Static plate electrode CJ _i, surface that ball-and-socket is relative with bulb all scribbles the high-abrasive material of self-lubricating property, as epoxy resin or teflon.

Described ball-and-socket adopts horizontal split type structure, comprises ball pivot seat and ball pivot end cap.

The material that described bulb selects electric conductivity good, as aluminum alloy.

Described static plate electrode CJ ₁, CJ ₄, CJ ₅and CJ ₈and relative static plate electrode CJ ₂, CJ ₃, CJ ₆and CJ ₇form the first differential capacitor group with bulb, can detect that bulb is relative to ball-and-socket offset δ in the X-axis direction _x.Static plate electrode CJ ₁, CJ ₂, CJ ₅and CJ ₆and relative static plate electrode CJ ₄, CJ ₃, CJ ₈and CJ ₇form the second differential capacitor group with bulb, can detect that bulb is relative to ball-and-socket offset δ in the Y-axis direction _y.Static plate electrode CJ ₁, CJ ₂, CJ ₃and CJ ₄and relative static plate electrode CJ ₅, CJ ₆, CJ ₇and CJ ₈form the 3rd differential capacitor group with bulb, can detect that bulb is relative to ball-and-socket offset δ in the Z-axis direction _z.

The beneficial effects of the utility model are:

1, the utility model changes the principle causing output capacitance to change according to the gap between sphere capacitor plate, arranges sphere capacitance detecting electrode, achieves the real-time online non-contact detection of spherical hinge Three Degree Of Freedom center displacement.

2, the utility model algorithm is simple and easy, and the differential capacitor group detection sensitivity that radius tip electrode is formed is high, can eliminate its mutual coupled relation, obtain the displacement component of three independent orthogonal after carrying out simple data processing to the signal obtained.

3, the utility model compact structure, precision are high, are easy to realize and equipment cost is low.

Accompanying drawing explanation

Fig. 1 is structural perspective of the present utility model;

Fig. 2 is the relative position stereogram of bulb and static plate electrode in the utility model;

Fig. 3 is the distribution schematic diagram that in the utility model, each static plate electrode is encircled into sphere;

Fig. 4 is the sectional arrangement drawing of static plate electrode and ball-and-socket in the utility model;

Fig. 5 is the mathematical model schematic diagram in bulb and ball-and-socket gap in the utility model.

Embodiment

Below in conjunction with drawings and Examples, the utility model is described in further detail.

As Fig. 1,2, shown in 3 and 4, detect the precision ball hinge of joint space based on sphere capacitance principle, comprise ball-and-socket, bulb 2-1, spherical hinge take-off lever 2-2 and static plate electrode; Static plate electrode CJ _ibe fixed in ball-and-socket, wherein, i=1,2 ... 8, and be distributed in eight quadrants of three-dimensional system of coordinate and be encircled into sphere; Static plate electrode CJ _ibe equal and opposite in direction and the radius tip electrode concentric with ball-and-socket; Ball-and-socket adopts horizontal split type structure, comprises ball pivot seat 1-1 and ball pivot end cap 1-2; Bulb 2-1 as movable plate electrode, and with static plate electrode CJ _iform eight sphere electric capacity 3; Spherical hinge take-off lever 2-2 and bulb 2-1 fixes.The material that bulb 2-1 selects electric conductivity good, as aluminum alloy; Static plate electrode CJ _iall insulating material is scribbled, as epoxy resin with the surface of contact of ball-and-socket; Static plate electrode CJ _i, surface that ball-and-socket is relative with bulb 2-1 all scribbles the high-abrasive material of self-lubricating property, as epoxy resin or teflon.When bulb 2-1 produces eccentric motion in ball-and-socket, change with the gap of static plate electrode thus cause the capacitance of each sphere electric capacity to change.

As shown in Figures 2 and 3, static plate electrode CJ ₁, CJ ₄, CJ ₅and CJ ₈and relative static plate electrode CJ ₂, CJ ₃, CJ ₆and CJ ₇form the first differential capacitor group with bulb 2-1, can detect that bulb is relative to ball-and-socket offset δ in the X-axis direction _x.Static plate electrode CJ ₁, CJ ₂, CJ ₅and CJ ₆and relative static plate electrode CJ ₄, CJ ₃, CJ ₈and CJ ₇form the second differential capacitor group with bulb 2-1, can detect that bulb is relative to ball-and-socket offset δ in the Y-axis direction _y.Static plate electrode CJ ₁, CJ ₂, CJ ₃and CJ ₄and relative static plate electrode CJ ₅, CJ ₆, CJ ₇and CJ ₈form the 3rd differential capacitor group with bulb 2-1, can detect that bulb is relative to ball-and-socket offset δ in the Z-axis direction _z.The theoretical calculation formula of offset can be expressed as:

$\left\{\begin{array}{c}{\mathrm{\δ}}_X=f_X(C_1+C_4+C_5+C_8-C_2-C_3-C_6-C_7)\\ {\mathrm{\δ}}_Y=f_Y(C_1+C_2+C_5+C_6-C_3-C_4-C_7-C_8)\\ {\mathrm{\δ}}_Z=f_Z(C_1+C_2+C_3+C_4-C_5-C_6-C_7-C_8)\end{array}\right.---\left(1\right)$

In formula, f _x, f _y, f _zrepresent the bulb 2-1 function along X, Y and Z axis change in displacement and capacitance variation respectively, its value is relevant to the structural parameter of electric capacity and the power gain of measurement processing circuit; C _irepresent static plate electrode CJ _iand the capacitance of the sphere electric capacity formed between bulb, wherein i=1,2 ... 8.

Can make:

$\left\{\begin{array}{c}\mathrm{\Δ}{C}_X=C_1+C_4+C_5+C_8-C_2-C_3-C_6-C_7\\ \mathrm{\Δ}{C}_Y=C_1+C_2+C_5+C_6-C_3-C_4-C_7-C_8\\ \mathrm{\Δ}{C}_Z=C_1+C_2+C_3+C_4-C_5-C_6-C_7-C_8\end{array}\right.---\left(2\right)$

Formula (1) can be reduced to:

$\left\{\begin{array}{c}{\mathrm{\δ}}_X=f_X\mathrm{\Δ}{C}_X\\ {\mathrm{\δ}}_Y=f_Y\mathrm{\Δ}{C}_Y\\ {\mathrm{\δ}}_Z=f_Z\mathrm{\Δ}{C}_Z\end{array}\right.---\left(3\right)$

As shown in Figure 5, in system of coordinates OXYZ, the unit vector of X, Y, Z axis is designated as respectively θ represents the angle of yaw of the relative Z axis of bulb 2-1,0≤θ≤π; represent the azimythal angle of the relative X-axis of bulb 2-1, bulb on the surface arbitrfary point P relative to the unit vector of the exterior normal OP of system of coordinates OXYZ is:

By static plate electrode CJ _idesirable Surface of Sphere is all considered as, if R with the opposing side of bulb ₀for the inner side surface spherical radius of static plate electrode, r is the radius of bulb, and δ is the linear displacement of the geometrical center O of the relative ball-and-socket of geometrical center O' of bulb.Therefore, the linear displacement vector of bulb bias can be expressed as:

$\stackrel{\→}{\mathrm{\δ}}={\mathrm{\δ}}_X\stackrel{\→}{i}+{\mathrm{\δ}}_Y\stackrel{\→}{j}+{\mathrm{\δ}}_Z\stackrel{\→}{k}---\left(5\right)$

In formula, δ _x, δ _y, δ _zbe respectively along the projection of X, Y, Z axis displacement.

The distance of intersection point Q to the P of the inner side surface sphere of O', P line and static plate electrode is the gap d at P point place, when bulb without acceptance of persons time primary clearance d ₀for:

d ₀＝PQ＝R ₀-r (6)

As shown in Figure 5, when bulb to have the offset of Three Degree Of Freedom relative to ball-and-socket, at δ " R ₀when, can be obtained by vector correlation:

$O^{\′}Q=\stackrel{\→}{O^{\′}Q}\·\stackrel{\→}{n}=(\stackrel{\→}{\mathrm{OQ}}-\stackrel{\→}{{\mathrm{OO}}^{\′}})\·\stackrel{\→}{n}=R_0-\stackrel{\→}{\mathrm{\δ}}\·\stackrel{\→}{n}---\left(7\right)$

Therefore, the gap d at P point place is

In order to simplify calculating, supposing that the sphere capacitance dC corresponding to unit dimension dA of static plate electrode such as is at the plate condenser in gap, and ignoring the edge effect of plate condenser.Therefore, the capacitance of every block sphere electric capacity 3 can utilize area integral formula to be expressed as:

$C_i=\mathrm{\ϵ}\underset{S_i}{\∫\∫}\frac{1}{d}\mathrm{dA},(i=\mathrm{1,2},...,8)---\left(9\right)$

In formula, ε represents the permittivity of material between bulb and ball-and-socket, S _irepresent static plate electrode CJ in sphere electric capacity 3 _ithe useful area of inner side, wherein, i=1,2 ... 8.

Make nominal electrode electric capacity s ₀represent the area of monolithic static plate electrode, introduce dimensionless electrode capacitance $c_i=\frac{C_i}{c_0};$ Introduce nondimensional quantity ${\mathrm{\λ}}_X=\frac{{\mathrm{\δ}}_X}{d_0},{\mathrm{\λ}}_Y=\frac{{\mathrm{\δ}}_Y}{d_0},{\mathrm{\λ}}_Z=\frac{{\mathrm{\δ}}_Z}{d_0}.$

Can be obtained by formula (8) and formula (9), static plate electrode CJ _iand the dimensionless electrode capacitance forming sphere electric capacity between bulb can be expressed as:

In formula, the electrode unit dimension that Q point is corresponding is

Due to the small eccentricity of spherical hinge, obtains according to Taylor series expansion:

By formula (10) and formula (11), then static plate electrode CJ _iand the dimensionless electrode capacitance forming sphere electric capacity between bulb can be reduced to:

In formula,

Consider the structure of static plate electrode and the symmetry properties of distribution, the integration variable θ in formula (10) and integrating range be:

$\mathrm{\θ}=\left\{\begin{array}{cc}[{\mathrm{\θ}}_0,{\mathrm{\θ}}_0+\mathrm{\Δ\θ}]& (i=\mathrm{1,2,3,4})\\ [\mathrm{\π}-{\mathrm{\θ}}_0-\mathrm{\Δ\θ},\mathrm{\π}-{\mathrm{\θ}}_0]& (i=\mathrm{5,6,7,8})\end{array}\right.---\left(13\right)$

In formula, θ ₀represent the initial angle of static plate electrode end face and Z axis forward, Δ θ represents the central angle on static plate electrode warp direction corresponding to arc length; represent the initial angle of each piece of static plate electrode same side and X-axis forward, represent the central angle corresponding to arc length on static plate electrode weft direction.

By θ and integration variable substitutes into formula (12) and obtains dimensionless electrode capacitance, then substitutes into the capacitance that following formula can obtain each sphere electric capacity 3 to be:

C _i＝c _i·C ₀(i＝1,2,…,8) (15)

Finally substitute into formula (2), calculate Δ C respectively _x, Δ C _y, Δ C _zvalue, thus set up the relation between differential capacitor value and center displacement amount.

The concrete numerical value now getting parameter further illustrates the process that this precision ball hinge detects joint space, and the limit pivot angle of the relative ball-and-socket of spherical hinge take-off lever is 10 °, θ ₀get Δ θ gets get get the dimensionless electrode capacitance value of each sphere electric capacity is obtained by formula (13), formula (14) and formula (12):

After calculating each dimensionless capacitance, substitute in formula (15).Because the offset of bulb in ball-and-socket is very little, therefore ignore the displacement composition of more than the second order of each axially eccentricity component and second order, arrangement can obtain:

$\left\{\begin{array}{c}{C}_1=\frac{C_0{R_0}^2}{S_0}(0.4251+0.2125{\mathrm{\λ}}_X+0.2125{\mathrm{\λ}}_Y+0.2777{\mathrm{\λ}}_Z)\\ C_2=\frac{C_0{R_0}^2}{S_0}(0.4251-0.2125{\mathrm{\λ}}_X+0.2125{\mathrm{\λ}}_Y+0.2777{\mathrm{\λ}}_Z)\\ C_3\frac{C_0{R_0}^2}{S_0}(0.4251-0.2125{\mathrm{\λ}}_X-0.2125{\mathrm{\λ}}_Y+0.2777{\mathrm{\λ}}_Z)\\ C_4=\frac{C_0{R_0}^2}{S_0}(0.4251+0.2125{\mathrm{\λ}}_X-0.2125{\mathrm{\λ}}_Y-0.2777{\mathrm{\λ}}_Z)\\ C_5=\frac{C_0{R_0}^2}{S_0}(0.4251+0.2125{\mathrm{\λ}}_X+0.2125{\mathrm{\λ}}_Y-0.2777{\mathrm{\λ}}_Z)\\ C_6=\frac{C_0{R_0}^2}{A_0}(0.4251-0.2125{\mathrm{\λ}}_X+0.2125{\mathrm{\λ}}_Y-0.2777{\mathrm{\λ}}_Z)\\ C_7=\frac{C_0{R_0}^2}{S_0}(0.4251-0.2125{\mathrm{\λ}}_X-0.2125{\mathrm{\λ}}_Y-0.2777{\mathrm{\λ}}_Z)\\ C_8=\frac{C_0{R_0}^2}{S_0}(0.4251+0.2125{\mathrm{\λ}}_X-0.2125{\mathrm{\λ}}_Y-0.2777{\mathrm{\λ}}_Z)\end{array}\right.---\left(17\right)$

Substitute into formula (2), calculate Δ C respectively _x, Δ C _ywith Δ C _zvalue, arrange:

$\left\{\begin{array}{c}{\mathrm{\δ}}_x=\frac{{{\mathrm{\δ}}_0}^2}{8\mathrm{\ϵ}{R_0}^2}\×\frac{1}{0.2125}\mathrm{\Δ}{C}_x\\ {\mathrm{\δ}}_y=\frac{{{\mathrm{\δ}}_0}^2}{8\mathrm{\ϵ}{R_0}^2}\×\frac{1}{0.2125}\mathrm{\Δ}{C}_y\\ {\mathrm{\δ}}_z=\frac{{{\mathrm{\δ}}_0}^2}{8\mathrm{\ϵ}{R_0}^2}\×\frac{1}{0.2777}\mathrm{\Δ}{C}_z\end{array}\right.---\left(18\right)$

Known according to formula (18), the relation between center displacement amount and differential capacitor value can be set up, and the decoupling zero achieving spherical hinge Three Degree Of Freedom center displacement is measured.

Static plate electrode CJ in actual measurement _iall access special signal processing circuit, after gathering, import the dynamic data that computer disposal can draw bulb and ball-and-socket gap into, achieve real-time online non-contact detection.This precision ball hinge structure is compact, and algorithm is simple, has larger future in engineering applications.

Claims (6)

1. detect the precision ball hinge of joint space based on sphere capacitance principle, comprise ball-and-socket, bulb, spherical hinge take-off lever and static plate electrode, it is characterized in that:

Static plate electrode CJ _ibe fixed in ball-and-socket, wherein, i=1,2 ... 8, and be distributed in eight quadrants of three-dimensional system of coordinate and be encircled into sphere; Static plate electrode CJ _ibe equal and opposite in direction and the radius tip electrode concentric with ball-and-socket; Described bulb as movable plate electrode, and with static plate electrode CJ _iform eight sphere electric capacity; Described spherical hinge take-off lever and bulb are fixed; Static plate electrode CJ _iall insulating material is scribbled with the surface of contact of ball-and-socket; Static plate electrode CJ _i, surface that ball-and-socket is relative with bulb all scribbles the high-abrasive material of self-lubricating property.

2. the precision ball hinge detecting joint space based on sphere capacitance principle according to claim 1, is characterized in that: described ball-and-socket adopts horizontal split type structure, comprises ball pivot seat and ball pivot end cap.

3. the precision ball hinge detecting joint space based on sphere capacitance principle according to claim 1, is characterized in that: described bulb selects conductive material.

4. the precision ball hinge detecting joint space based on sphere capacitance principle according to claim 1, is characterized in that: described static plate electrode CJ ₁, CJ ₄, CJ ₅and CJ ₈and relative static plate electrode CJ ₂, CJ ₃, CJ ₆and CJ ₇form the first differential capacitor group with bulb, can detect that bulb is relative to ball-and-socket offset δ in the X-axis direction _x; Static plate electrode CJ ₁, CJ ₂, CJ ₅and CJ ₆and relative static plate electrode CJ ₄, CJ ₃, CJ ₈and CJ ₇form the second differential capacitor group with bulb, can detect that bulb is relative to ball-and-socket offset δ in the Y-axis direction _y; Static plate electrode CJ ₁, CJ ₂, CJ ₃and CJ ₄and relative static plate electrode CJ ₅, CJ ₆, CJ ₇and CJ ₈form the 3rd differential capacitor group with bulb, can detect that bulb is relative to ball-and-socket offset δ in the Z-axis direction _z.

5. the precision ball hinge detecting joint space based on sphere capacitance principle according to claim 1, is characterized in that: described insulating material is epoxy resin; Described high-abrasive material is epoxy resin or teflon.

6. the precision ball hinge detecting joint space based on sphere capacitance principle according to claim 3, is characterized in that: described conductive material is aluminum alloy.